GRASSES OF IOWA. 39 



sandy soil. The cells of Eragrostis purshii vary considerably 

 in size, being smaller above or below the bundles than those 

 adjacent to the mesophyll. 



In Sporobolus cryptandrus* the cells have a particularly well 

 developed cuticle. Miss Ogden describes a most peculiar kind of 

 epidermal cells in Eragrostis obtusiflora with curved, beak- like 

 expansions that project from the stomata; the cells are very 

 unevenly thickened. 



Scent glands. — Another most interesting feature to be added 

 to the epidermal layer is the peculiar glands which grow on 

 certain grasses. Oae of the best known illustrations of glan- 

 dular trichomes in grasses occurs in the common stink grass 

 (Eragrostis major). These glands were first studied by Pro- 

 fessor Trelease. f 



The somewhat similar glands of Sporobolus heterolepeis had 

 previously been studied by C. E. Bessey. X 



Recently Mr. C. R. Ball has studied the glands of Eragrostis 

 major. The following is condensed from papers by Mr. Ball 

 and Professor Trelease. The small projections, or scent 

 glands as they are known, are epidermal structures consisting 

 of the single layer of cells. Those at the center are consider- 

 ably elongated and the parenchyma cells are provided with 

 thick-pitted walls. Those in the center are much thinner- 

 walled. As compared with the unmodified epidermal cells, 

 these elongated glandular cells are also thin-walled at top, 

 where, in common with the other elements of the epidermis, 

 they are invested with a rather heavy cuticle. In some cases 

 this membrane is seen to be free from the crater of the gland 

 in the form of a blister, while in others it has been ruptured, 

 so that only fragments are present. Miss Ogden describes 

 glandular bodies as occurring in Eragrostis obtusiflora. In her 

 description it is stated that these glands are provided with a 

 narrow neck and a capitate exodermal portion. 



Fig. 30. Scent glands of stink grass (Eragrostis major). Figure to right, surface 

 view; left view In section, (Ball.) 



♦Emma Slrrlne and Emma Pammel, 1. c. 153. 



tThe glands of Eragrostis major Host. Proc. Soc. Proc. Agrl. Scl., 10: 70. 1889. 



*Glands on a grass. Am. Nat., 18: 430, /. 1. 1884. 



